518 Experimental Studies on the Origin of the Lens in Amphibia 



l}dng ectoderm and modification of the inner layer indicate the ectoder- 

 mal origin of the lens. 



Experiment DF^-. 



The embryo was killed four days after the operation. The regener- 

 ated right eye is of medium size and is separated from the ectoderm by 

 a layer of mesenchyme, see Fig. 21. The lens which is about 70/^ in 

 diameter lies in the optic cup and has apparently just separated from 

 the inner layer of the ectoderm from which there is a small irregular 

 projection corresponding to an • irregularity on the superficial surface of 

 the lens. The transplanted eye which lies just caudal to the regenerated 

 eye is as large as the normal one on the left side. It is separated from 



Fig. 20. Fig. 21. Fig. 22. 



Fig. 20. Experiment DF13. Section tliroug-h transplanted eye and lens. X 50 diameters. 



Fig. 21. Experiment DF45. Section through regenerated eye and lens. X fJO diameters. 



Fig. 22. Experiment DF45. Section through transplanted eye and lens. X 100 diameters. 



the ectoderm by a thin layer of mesenchyme. Fig. 22 is from a section 

 through the cephalic end of the eye and shows between the outer layer 

 of the optic cup and the ectoderm a lens about SO/x in diameter. It is 

 impossible to determine the exact origin of this lens but the preceding 

 and succeeding experiments clearly indicate that it is of ectodermal 

 origin. 



Experiment DF^.^. 



The embryo was killed four days after the operation. The sections 

 show a rather deeply seated medium sized regenerated eye, see Pig. 23. 

 Tlie small lens is still attached to the inner layer of the ectoderm by a 

 long narrow pedicle which extends throvtgh the rather thick layer of mes- 

 enchyme separating the optic cup and skin. Had the embryo been killed 



